Fluorescence-based optical sensor design for molecularly imprinted polymers

A Monte Carlo model was developed to analyze the sensitivity and the performance of a fluorescence-based molecularly imprinted polymer (MIP) sensor. The MIP sensor consisted of highly cross-linked polyurethane containing anthracene binding sites coated on a transparent substrate. The optical properties of MIPs, the quantum yields of anthracene within MIPs, and the fluorescence of MIPs were measured. The rebinding capacity of the MIPs was about 1 μmol/g or roughly seven times binding rate of non-imprinted polymers. The MIP fluorescence emission at 404 nm was measured for thicknesses ranging from 100 to 2000 μm containing templated anthracene concentrations ranging from 60 to 600 ppm for excitation at 358 nm. The emission agreed with model predictions within 15%. This sensing system could only distinguish anthracene down to 15 ppm due to fluorescence from the polymer matrix. To make a fluorescence-based MIP sensor that is capable of detecting one part per billion analyte concentration with a 200 μm thick MIP film, our model suggests that imprinted polymers would need to have an absorption coefficient less than 0.001 cm−1, or have a quantum yield 105 times lower than that of the analyte at the detection wavelength.